1. Technical Field of the Invention
The present invention relates to an aqueous dispersion containing polymer particles and inorganic particles. The polymer particles and inorganic particles in the aqueous dispersion of the present invention are included as composite particles (aggregates). The composite particles of the present invention have adequate strength and hardness and excellent heat resistance, and the aqueous dispersion can be utilized for cosmetics, electronic materials, magnetic materials, coating materials, paints, optical materials, catalysts, photocatalysts, electronic material film lubricants, diagnostic agents, drugs, conductive materials, inks and the like, and can also be used as a polishing material for magnetic disks and the like.
Another aspect of the present invention relates to an aqueous dispersion for chemical mechanical polishing (hereunder referred to as xe2x80x9cCMPxe2x80x9d) employed in the manufacture of semiconductor devices. More specifically, the present invention relates to an aqueous dispersion that is useful for CMP of semiconductor device working films, and that contains polymer particles, inorganic particles and water, wherein the zeta potentials of the particles are of opposite signs.
Yet another aspect of the present invention relates to an aqueous dispersion containing water and composite particles that consist of polymer particles and inorganic particles bonded by electrostatic force, and to an aqueous dispersion that is suitable for CMP of semiconductor device working films.
Still another aspect of the present invention relates to an aqueous dispersion containing composite particles wherein the polymer particles and inorganic particles have zeta potentials of opposite signs and the particles are bonded by electrostatic force, and to an aqueous dispersion that is suitable for CMP of semiconductor device working films.
Still another aspect of the invention relates to a method for manufacture of semiconductor devices, and more specifically to a method for formation of embedded wiring mounted on DRAMs and high-speed logic LSIs by CMP and to a method for manufacture of semiconductor devices using the technique.
2. Prior Art
For such uses as standard particles, diagnostic agent carrier particles, lubricants and the like, it has been conventional to use polymer particles with a narrow particle size distribution obtained by copolymerizing vinyl monomers or the like, in such forms as aqueous dispersions. However, the polymer particles do not always have sufficient strength and heat resistance, and when used as standard particles or lubricants, application of excessive shear stress or exposure to high temperature can cause deformation or destruction of the particles, and therefore their uses are limited. In order to deal with these problems there have been proposed particles made of copolymers of crosslinkable vinyl monomers, for example, that are copolymerized with a high degree of crosslinking. However, particles made of such crosslinked polymers have lower hardness and insufficient heat resistance compared to inorganic-based particles, and therefore cannot be made into aqueous dispersions that are suitable for a very wide range of uses.
For uses such as electronic materials, magnetic materials, optical materials, polishing materials and the like there have been employed aqueous dispersions containing particles made of various metal compounds, and a variety of composite particles have been proposed for diverse purposes. As such types of composite particles there may be mentioned composite particles comprising iron oxide particles coated with silicon compounds, so that in production of filamentous magnetic bodies by heat treatment it is possible to prevent shape collapsing and sintering between magnetic bodies; composite particles comprising iron powder coated with copper as a high strength material for powder metallurgy; and composite particles comprising iron oxide particles coated with antimony oxide and aluminum oxide for improved heat resistance. However, since such composite particles are all composed of metal compounds, they are too hard and are not always adequately suited for diverse purposes. The development of composite particles with appropriate hardness has thus become a necessity particularly in the fields of electronic materials, magnetic materials, optical materials, polishing materials, and so forth.
Improvements in degrees of semiconductor device integration and increased multilayer wiring have led to the introduction of CMP techniques for polishing of working films and the like. As disclosed in Japanese Laid-open Patent Publication No. Sho-62-102543, No. Sho-64-55845 and No. Hei-5-275366, Japanese Patent Public Inspection No. Hei-8-510437, and Japanese Laid-open Patent Publication No. Hei-8-17831, No. Hei-8-197414 and No. Hei-10-44047, there are known methods whereby wiring is formed by embedding a wiring material such as tungsten, aluminum or copper in a hole or trench formed in the insulation film of a process wafer, and then polishing to remove the excess wiring material.
In CMP it has been conventional to use polishing materials that are aqueous dispersions containing abrasive particles made of metal oxides. However, these abrasive particles present a problem in that their high hardness creates scratches in the polishing surface. Such scratches created during the CMP step are undesirable because they lower the reliability of the resulting LSI. In order to prevent creation of such scratches, Japanese Laid-open Patent Publication No. Hei-9-285957 has proposed a polishing material comprising abrasive particles such as colloidal silica, and including scratch-preventing particles made of polyurethane resin or the like with a larger particle size than the abrasive particles. However, using polishing materials containing scratch-preventing particles with a large particle size and low hardness has resulted in the problem of vastly reduced polishing rate compared to polishing materials containing metal oxide abrasive particles.
In recent years, more attention is being focused on achieving lower permittivities of interlayer insulation films for the purpose of improving VLSI performance. For lower permittivity there have been developed interlayer insulation films comprising fluorine-containing SiO2 (permittivity: approximately 3.3-3.5), polyimide-based resins (permittivity: approximately 2.4-3.6, trade name xe2x80x9cPIQxe2x80x9d by Hitachi Chemical Industries Co., Ltd.; trade name xe2x80x9cFLARExe2x80x9d by Allied Signal Corporation, and the like), benzocyclobutene (permittivity: approximately 2.7, trade name xe2x80x9cBCBxe2x80x9d by Dow Chemical Corporation, and the like), hydrogen-containing SOG (permittivity: approximately 2.5-3.5) and organic SOG (permittivity: approximately 2.9, trade name xe2x80x9cHSGR7xe2x80x9d by Hitachi Chemical Industries Co., Ltd.) and the like, instead of high-permittivity SiO2 films. However, because these insulation films have lower mechanical strength than SiO2 films and are soft and brittle, polishing by using conventional aqueous dispersions containing inorganic particles has resulted in wire breakage by creation of scratches, and this has led to further decreasing yields.
Japanese Laid-open Patent Publication No. Hei-7-86216 describes a polishing material containing abrasive particles composed mainly of an organic polymer compound or the like instead of abrasive particles made of a metal oxide. It is explained that using the polishing material for polishing of semiconductor device working films can prevent generation of scratches in polishing surfaces. However, abrasive particles made of such organic polymer compounds have low hardness, and polishing materials containing these abrasive particles as main components also give vastly lower polishing rates compared to polishing materials containing abrasive particles made of metal oxides.
Thus, the materials described in these publications cannot achieve highly reliable high-speed polishing of working films in the manufacture of semiconductor devices, nor do they allow highly efficient fabrication of semiconductor devices.
In recent years, the field of semiconductor device manufacture has seen increased miniaturization and higher density, and this has led to research and development of a variety of microengineering techniques. One of these techniques, CMP is an important indispensable technique for formation of embedded metal wiring (damascene wiring).
According to the prior art, techniques for polishing of metals by CMP (metal CMP) have employed slurries based on inorganic particles such as alumina or silica. Here, hard polishing pads with low elastic deformation are used in order to control erosion, but since the elasticity of the abrasive particles themselves is poor, a problem occurs as scratches are produced in the wiring. In addition, the abrasive grains concentrate in the scratches so that the scratched portions are enlarged making it impossible to control erosion.
On the other hand, research is also progressing on slurries using polymer particles such as resins. Polymer particles are characteristically softer than inorganic particles. This provides an advantage since the particles themselves exhibit elasticity, thus allowing scratches to be avoided even when a hard polishing pad is used. However, because the particles have virtually no polishing ability, slurries employing polymer particles alone have not been of a practical level.
It is an object of the present invention to overcome the aforementioned problems of the prior art by providing an aqueous dispersion containing composite particles that are aggregates of polymer particles and inorganic particles, and exhibit sufficient strength and hardness, excellent heat resistance and appropriate plasticity. The aqueous dispersion is useful for a wide range of purposes including electronic materials, magnetic materials and optical materials, and can be used for polishing of magnetic disks and the like.
It is an object of another aspect of the present invention to overcome the aforementioned problems of the prior art by providing an aqueous dispersion for CMP (hereunder referred to as xe2x80x9cCMP aqueous dispersionxe2x80x9d) that can accomplish polishing of semiconductor device working films at an adequate rate, and that can be used in the manufacture of semiconductor devices without creating scratches in polishing surfaces.
It is another object of the present invention to provide a method for manufacture of semiconductor devices using a CMP slurry that can control progressive erosion due to scratches and the like during polishing, and that can achieve efficient flattening of working films.
It is still another object of the present invention to provide a method for formation of satisfactory embedded wiring that can control progressive erosion due to scratches and the like during polishing, and that can achieve efficient flattening of working films.
The present invention has been accomplished upon the discovery that in an aqueous dispersion containing specific polymer particles and inorganic particles, adjustment of the pH for an aqueous dispersion wherein the polymer particles and inorganic particles have zeta potentials of opposite signs results in electrostatic aggregation of these particles causing them to combine together, to give an aqueous dispersion that is useful for the various purposes mentioned above.
An aqueous dispersion according to the first aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the zeta potential of the polymer particles and the zeta potential of the inorganic particles are of opposite signs.
An aqueous dispersion according to the second aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the polymer particles and the inorganic particles are electrostatically bonded to form composite particles.
An aqueous dispersion according to the third aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the zeta potential of the polymer particles and the zeta potential of the inorganic particles are of opposite signs, and the polymer particles and the inorganic particles are electrostatically bonded to form composite particles.
An aqueous dispersion according to the fourth aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the zeta potential of the polymer particles and the zeta potential of the inorganic particles are of opposite signs, the polymer particles and the inorganic particles are electrostatically bonded to form composite particles, the composite particles are obtained after ultrasonic irradiation treatment or mechanical shear stress treatment with a homogenizer, and the mean particle size of the composite particles is not greater than 1 xcexcm.
A CMP aqueous dispersion used for the manufacture of semiconductor devices according to the fifth aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the zeta potential of the polymer particles and the zeta potential of the inorganic particles are of opposite signs.
A CMP aqueous dispersion used for the manufacture of semiconductor devices according to the sixth aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the polymer particles and the inorganic particles are electrostatically bonded to form composite particles.
A CMP aqueous dispersion used for the manufacture of semiconductor devices according to the seventh aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the zeta potential of the polymer particles and the zeta potential of the inorganic particles are of opposite signs, and the polymer particles and the inorganic particles are electrostatically bonded to form composite particles.
A CMP aqueous dispersion used for the manufacture of semiconductor devices according to the eighth aspect of the present invention is characterized by containing polymer particles, inorganic particles and water, wherein the zeta potential of the polymer particles and the zeta potential of the inorganic particles are of opposite signs, the polymer particles and the inorganic particles are electrostatically bonded to form composite particles, the composite particles are obtained after ultrasonic irradiation treatment or mechanical shear stress treatment with a homogenizer, and the mean particle size of the composite particles is not greater than 1 xcexcm.
A method for manufacture of semiconductor devices according to the ninth aspect of the present invention is characterized by using a CMP slurry containing aggregates comprising polymer particles and inorganic particles adsorbed onto the polymer particles.
A method for manufacture of semiconductor devices according to the tenth aspect of the present invention is characterized by using a CMP slurry containing aggregates comprising polymer particles, a surfactant adsorbed onto the polymer particles, and inorganic particles adsorbed onto the surfactant.
A method for formation of embedded wiring according to the eleventh aspect of the present invention is characterized by using a CMP slurry containing aggregates comprising polymer particles and inorganic particles adsorbed onto the polymer particles.
A method for formation of embedded wiring according to the twelfth aspect of the present invention is characterized by using a CMP slurry containing aggregates comprising polymer particles, a surfactant adsorbed onto the polymer particles, and inorganic particles adsorbed onto the surfactant.
When an aqueous dispersion according to the present invention is used for polishing of various polishing films, the polishing rate is high and there is no scratching of the polishing surface. The aqueous dispersion of the present invention is useful for a wide range of purposes including electronic materials, magnetic materials and optical materials, and can be used as a polishing material for polishing of magnetic disks and the like.
When a CMP aqueous dispersion according to the present invention is used as a polishing material for polishing of semiconductor device working films, the polishing rate is high and there is no scratching of the polishing surface.
By applying the method for manufacture of semiconductor devices or the method for formation of embedded wiring of the present invention it is possible to suppress progressive erosion during polishing due to scratching and the like, and to achieve more efficient flattening of working films.
As a result, it is possible to stably form embedded wiring with low scratching and erosion, thus allowing highly reliable semiconductor devices to be obtained more easily.